1. Field of the Invention
The present invention relates to a signal processing technology applied to an imaging apparatus such as an electronic camera, a video camera, a scanner and a printer.
2. Description of the Related Art
In general, an imaging apparatus has something that applies a spatial frequency filter to a pixel signal in order to perform edge enhancement and noise reduction.
For example, as a spatial frequency filter for noise reduction, there is known a method in which a 3×3 pixel block around the pixels of the processing object is cut out, having the pixels of the processing object in the center, the pixel block is multiplied by a coefficient group of    1 1 1    1 2 1    1 1 1,and a weighted average is taken.
Besides, for example, as a spatial frequency filter for edge enhancement, there is known a method in which a 3×3 pixel block around the pixels of the processing object is cut out, having the pixels of the processing object in the center, the pixel block is multiplied by a coefficient group of    −1 −1 −1    −1 9 −1    −1 −1 −1,and addition is done.
It is also publicly known that the intensity of the noise reduction and edge enhancement can be adjusted by performing adjustments (including size adjustment of the pixel blocks) of these coefficient groups.
Japanese Unexamined Patent Publication No. Hei. 5-174142 discloses a technique in which a pixel signal of a processing object is decomposed into signals of lightness, color saturation and hue, and edge enhancement and edge relaxation are performed for the signals of lightness and color saturation.
In the foregoing related arts, edge enhancements and the noise reductions are uniformly performed for all pixels. Thus, it had been necessary to perform edge enhancement and noise reduction moderately so that failures do not occur in processing results of images of various patterns. Thus, sufficient signal processing could not be performed for places where edge enhancement is desired to be actively performed or places where noise reduction is desired to be performed more intensely, and so it had been difficult to obtain optimum processing results.